So long as there's rhyme and reason to the numbering scheme, I have no problem with it.
BMW does this, and it's awesome. The first digit is the body style (3 is small, 5 is mid, 7 is large), and the next 2 digits are the engine displacement.
Except when they aren't; these days, the next 2 digits may, or may not, have any connection to the engine size. For example, both the BMW UK page giving technical data for the 3 series and the BMW USA page for building your own car, after selecting the 3 series sedan indicate that both the 320i and the 330i have a 2-litre turbo 4, with the 330i just having a more powerful version.